The present invention relates to a technique for an audio and video device system (hereinafter referred to as “the AV device system”) including at least two AV devices having the audio information reproducing function, the video information reproducing function, etc. connected by a bus, or more in particular to a device application technique to secure the use of a plurality of AV devices operatively interlocked with each other.
The present invention also relates to an audio and video device system (hereinafter referred to as “the AV system”) comprising a plurality of AV devices interconnected by a bus, or more in particular to a plurality of devices and a device configuration of an AV system which are managed by timer for reservation of the operation of the devices of the AV system.
A communication system using an IEEE1394 serial bus or a USB (Universal Serial Bus) has been proposed as a system including a video tape recorder (VTR), a TV receiver (TV) or other AV devices and information processing units connected by a control bus capable of transmitting and receiving both data and control signals between the devices.
The IEEE1394 serial bus can support both the isochronous transfer of such data as digital AV signals continuously at a predetermined bit rate and the asynchronous transfer of control signals such as connection control commands as required.
In addition to the isochronous transfer described above, the USB also permits a control transfer used for transmission and receipt of messages and the bulk transfer of a large amount of data at a bit rate not guaranteed.
In a system using the IEEE1394 serial bus or USB, a node ID is allocated automatically in accordance with the manner of connection of each device. Also, when a new device is added to or a device is removed from the system, the bus is reset and a node ID is allocated automatically again in accordance with the new connection.
Further, standardization is under way of control signals “AV/C Digital Interface Command Set” for controlling various AV devices from an external source.
Under the circumstances, when a system is constructed of various AV devices interconnected by the IEEE1394 serial bus or the USB to communicate data and control signals, there may be the case in which a given AV device controls other AV devices. A typical function is securing the use of a device by timer reservation for recording or reproduction.
In the conventional timer reservation functions, however, related AV devices are operated individually by the operators for timer reservation, and each AV device has never participated in the operation of other AV devices. When a set time arrives, therefore, each AV device outputs AV data such as image or audio information or starts the recording operation, for example, regardless of the operating condition of a related AV device. In the conventional method, therefore, before setting a reservation by timer, the operator is required to check whether each related device is operable at the reserved time.
If the time on the clock built in each device is not correct or the clock is cleared or stopped due to a power failure or the like, unintended AV data may be recorded, part of the intended AV data may fail to be recorded, or otherwise normal recording may become impossible.
Further, assume that a fee-charging program such as broadcast by a satellite is recorded by timer reservation. In the case where the on-air time of the program is unexpectedly extended, a VTR terminates the recording operation against the will of the operator with the arrival of the scheduled time set in advance, even though the integrated receiver/decoder may be able to meet the situation.
When a fee-charging program is reserved for recording by timer, the operator inserts a recording medium (tape or disk) having a recording area required for recording the particular program. In spite of this, the tape or disk may be taken out or used for recording a different program before the reserved time. The probable result is the shortage of the recording area, thereby making the normal recording of the reserved program impossible.